Radio frequency identification (RFID) products have been widely used in many fields, such as warehouse management, container management, medical management, animal management or door access management and so on. One of the latest applications is the electronic shelf label (ESL) system, as disclosed in U.S. Patent Publication No. 2004/0035937. However, in the above applications, a host system used to receive and transmit the signals, and a number of RF transponders are required. In certain cases, such as ESL systems, the RF transponders do not only reply the identification request from the host system but also display the images required by the host system. Therefore, generally, in such a situation, the RF transponders need a display to immediately update the current image based on the request of the host system. For examples, the updated price and the inventory are displayed.
However, this kind of RF transponder equipped with a display needs the additional electric power to drive the display. The well-known method for providing the additional electric power includes using an external power supply such as a battery. Although using the battery has more advantages and higher practicability, the lifespan of the best battery currently available lasts at least 3-5 years. That is, the RF transponder powered by the battery needs to spend money and manpower to change the battery periodically. No doubt, for the shopping mall adopting ESL systems, this is a heavy financial burden. Furthermore, during the period of replacing the exhausted battery, the trade in the market is badly affected somewhat.